With respect to extermination of insect pests, various methods of exterminating insect pests have been developed. In particularly, since termites seriously damage wooden houses, an agent for and a method of exterminating the termites have been researched and developed throughout the world. As the method of exterminating the termites, a method of exterminating the termites by injecting a solution-type drug, such as an organophosphate, a carbamate, a pyrethroid, into sites which the termites intrude, or a method of exterminating the termites by fumigation of methyl bromide and the like (for example, see Non-Patent Document 1).
As an alternative to the treatment method based on spraying pesticides, a bait method is known in which slow-acting, insecticidal active ingredients are mixed into a bait, and the bait is allowed to be eaten by termites, thereby exterminating them (See, for example, Non-Patent Document 2).
Techniques which have been heretofore used for exterminating insect pests, especially termites, are those that basically, a large amount of insecticide is put in from the outside of insect pest-damaged wood so as to exterminate the insect pests, and thus lead to health damages to human body and environmental pollution. In addition, there is a problem that damages are spread in other places when even a portion of the termites' colony remains surviving. It is the most serious problem that labor costs required for extermination with these techniques are too high. The method for exterminating insect pests which is frequently carried out is a fumigation process using methyl bromide, but it is a substance causing the destruction of the ozone layer and thus, in these days, results in enhanced movements to regulate its use.
As methods for exterminating ants which organize a social life as with the termites, a method is effective, in which a bait that an ants' favorite food is mixed into poisonous materials is given to ants and allowed to be taken back into their nest, thereby killing the whole population within the nest. However, the bait method in which poisonous baits are employed for allowing termites to transport insecticides from the outside to the inside of their nest are not always effective, because termites eat wood itself where they build a nest. In particular, it is difficult to completely exterminate termites of the genus Reticulitermes by the bait method (see, for example, Non-Patent Document 2).
As a method of more efficiently allowing insect pests to ingest an active ingredient than the bait method, “a method of exterminating insect pests by transportation of an imitation egg” using an instinct to transport eggs that is basic social behavior of insect pests have been developed (Patent Document 1). The insect pests in this method were termites. In this method, it was possible to allow termites to transport imitation eggs using crude extractives from eggs of termites, but an egg recognition pheromone of termites was not identified. There is a big problem in terms of cost to carry out such a method unless a large amount of the egg recognition pheromone can be inexpensively produced by identifying the egg recognition pheromone.
The present inventors identified that a main component of the egg recognition pheromone was a lysozyme, a lysozyme salt, a biological fragment of a lysozyme or a lysozyme-related peptide, and proposed an imitation egg formed by a combination of the egg recognition pheromone and an agent for exterminating termites (Patent Document 2). The imitation egg was transported in a nest by the termites, and it was recognized that effects of exterminating the termites were accomplished. However, since the agent for exterminating termites is present on the surface of the imitation egg, a transporting rate of the imitation egg by the termites is not sufficient. In addition, since there was a possibility adversely affecting a human being, which uses the agent for exterminating the insect pests and a method of exterminating insect pests by using the agent, and domestic animals and useful insects around the human being, safety was not sufficient, and there was a room to further enhance a performance as an agent for exterminating insect pests.
The present inventors studied a type of a substrate of the imitation egg, and confirmed the fact that a transporting rate of the imitation egg by the termites is very high in case of inorganic materials, particularly a glass as the substrate and a transporting rate which is as high as the rate in case of the glass was not obtained in case of other materials. However, it is difficult to contain an active ingredient for exterminating insect pests in the imitation egg, of which the substrate is an inorganic material. Therefore, in case of using only glass beads, since it is necessary to directly apply the active ingredient for exterminating insect pests as an agent on the surface of the glass beads, there is a limit to the agent amount that can be applied. In addition, since termites evade the agent, the termites do not transport the glass beads. An egg recognition pheromone of termites is also applied on the surface of the glass beads, but it is difficult to fix the egg recognition pheromone thereon. Therefore, when humidity is high in an installation location of the imitation eggs, since the egg recognition pheromone is easily carried away with water due to dew condensation on the surface of the glass beads, the termites do not recognize the glass beads as eggs of the termites, and the termites do not transport the glass beads. In order to solve the problems, the present inventors proposed an agent for exterminating insect pests, of which an active ingredient for exterminating insect pests is formed into a capsule of a material such as gelatin that the active ingredient is easily contained and is mixed with the imitation eggs (Patent Document 3). However, in the above technology, since the imitation eggs containing no active ingredient for exterminating insect pests are mixed with the capsules containing the active ingredient, there is a room to improve an efficiency of exterminating insect pests.